Human morphological variation has been described in previous research as reflecting and responding to environmental factors. Among Europeans and Africans, cranial and postcranial morphologies form clines in their variation across latitude and, by extension, climate. Subsistence practices have also affected variation in some of these morphologies:​ for example, the adoption of agriculture may have led to decreases in stature. Some of these morphological patterns have been reported in the examination of native humans in the Americas, though much variation in the New World has been unexamined.

This dissertation compares human morphological variation in the Americas with climatic and subsistence factors. A total sample of 3199 pre-contact adult skeletons, representing the majority of the Holocene in North America and some sites from South America, was measured. Up to 143 linear osteometric measurements were taken on crania and postcrania, and used to recreate the proportions and living dimensions of these individuals. These morphologies were compared within and across regions through time. Their variation was then compared with temperature and precipitation modeled using paleoclimatic data, and with subsistence categories based on archaeological evidence.

Results indicated that humans were morphologically varied through the entirety of the Holocene in the Americas. As expected, cranial, nasal, brachial and crural indices, and body breadth corresponded to variation in climatic factors but not with subsistence. Variation in relative torso height and facial index unexpectedly did not relate to environmental factors. Stature variation corresponded to subsistence, and body mass to both climate and subsistence. Analyses indicated that climate and subsistence were inexorably linked, but that many morphologies did not vary among subsistence practices. Body breadth and crural index varied less in relation to climate than brachial and nasal indices. Furthermore, all samples from the New World were wider-bodied than Old World samples, while having a similar range of variation in intralimb indices. These results indicate different amounts of morphological response to environmental factors, and therefore retained population history in some morphologies, such as body breadth. This history has affected samples from the arctic and the Great Plains, which show extremely different morphological patterns from the rest of the Americas